1. Technical Field.
This invention relates generally to laminated structures, and more particularly to a glass laminated structure suitable for use as a thermal energy barrier.
2. Background Information.
U.S. Pat. No. 4,439,392 to Schutzler et al. describes a glass laminated structure suitable for blocking high intensity thermal radiation such as might result from a nuclear blast. It is fabricated according to a novel method which includes retaining first and second panels against first and second platens, introducing a photochromic epoxy material between the panels, and curing the epoxy to produce the laminate.
The laminated structure of the Schutzler et al. patent includes glass panels that abut generally coplanar frame members that circumscribe the panel peripheries in end-to-end relationship, and deformable seals disposed between the panels and frame members that seal the panel-frame interface. This arrangement provides the desired peripheral framework sealed to the glass panels, but it results in the epoxy-panel interface that tends to delaminate under certain extreme temperature conditions.
The tendency to delaminate results from the different thermal coefficients of expansion exhibited by the epoxy core and the glass panels. This difference produces stresses that translate to a shearing force couple at the epoxy-panel interface of sufficient magnitude to defeat the bond. The stresses are not adequately absorbed so that defective structures may result. Consequently, it is desirable to have a new and improved glass laminated structure that overcomes this concern.
The method and tooling of the Schutzler et al. patent are very effective and applicable to the making of the improved glass laminated structure of this invention. However, certain aspects of the laminating process and tooling described in the Schutzler et al. patent could be made even better. For example, the elongated grooves for retaining the glass against the platens tend to result in the glass deforming into the groove. Also, the vacuum grease used in sealing the glass panels against the platens sometimes contaminates the inner panel surfaces that are to be bonded to the epoxy core, and this impairs the bond.
The silicone sealing material used as a seal between the glass panels and the frame also contaminates the inner panel surfaces occasionally. In addition, it takes relatively long to cure. Furthermore, tape is often used to seal the outer edges of the frame, and this takes additional time and care. Therefore, it is desirable to have an improved laminating apparatus and methodology that overcomes these concerns also.